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Smoke from wildfires in Canada and Minnesota engulfs the Washington, D.C., skyline, reducing visibility and casting a haze over the U.S. Marine Corps War Memorial on Friday.Finn Gomez/Getty Images
U.S. President Donald Trump is blaming Canadian forest management for the smoke that has blanketed parts of the United States, threatening to increase tariffs to compensate for U.S. expenses caused by plummeting air quality.
But a wildfire expert says the President’s claims lack grounding in science and excoriated the remedies aimed at Canada as being unreasonable.
In a Truth Social post Friday, Mr. Trump wrote that he would “hold Canada responsible” for not “properly managing their Forests.”
“Canada has refused to engage in basic Forest Management and Debris Removal,” the President wrote, claiming cross-border smoke was costing the U.S. “Billions of Dollars,” which would be added to tariffs he claimed Canada is currently paying.
The U.S. President said he would call Prime Minister Mark Carney on Friday to discuss the issue, and made no concrete proposal for what tariffs, if any, he could apply. The U.S. Supreme Court, in a ruling earlier this year, constrained Mr. Trump from summarily imposing tariffs on an emergency basis. Mr. Carney’s office did not return a request for comment.
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The move comes two days after Republican congress members from Michigan claimed in a letter to Mr. Carney that the fires are “a crisis that Canada has the tools to prevent and has chosen not to.”
“American lungs are paying the price for Canadian inaction on wildfires, year after year,” they wrote.
The four authors of the letter did not respond to requests for comment.
Bob Gray, a Chilliwack, B.C.-based certified wildfire ecologist, said the U.S. complaints sidestep the fact that wildfire smoke routinely crosses the border in both directions.
“We trade smoke back and forth across the border all the time,” said Gray, who started his career decades ago as an elite wildland firefighter in the U.S.
He pointed to 2020, when smoke from fires in the western U.S. choked Vancouver’s harbour. In 2023, a fast-moving wildfire roared across the border from Washington state into Osoyoos, B.C. and nearly wiped out several subdivisions. And blazes in Minnesota crossed the border into Ontario earlier this year.
Mr. Gray said given the extreme conditions under which the Ontario fires exploded, there was never a real prospect of putting them out.
The majority of the fires were ignited around July 12 by a lightning storm across the region. The Fire Weather Index, a numerical rating of potential fire intensity, was off the charts. Forest fuels were so dry that virtually everything would have been available to burn. Another indicator measuring the expected severity reached the top of existing scales, making it far too dangerous to put firefighters on the ground.
“You can’t fight those fires,” Mr. Gray said.
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Smoke clouds the sky near the Brooklyn Bridge in New York City, above, and on the Toronto Islands earlier this week.COLE BURSTON/AFP/Getty Images
High wind speeds pushing the fires across largely flat boreal forest meant that even air assets like water bombers and helicopters would likely not have worked, Mr. Gray said.
Canadian fire crews battle wildfires using roughly the same tactics and strategies of their U.S. counterparts, Mr. Gray said.
In recent years, Canada has moved away from aggressively suppressing all wildfires, instead choosing what’s called a “modified response” in some cases where conditions indicate fires can be safely left to burn, which is also similar to the U.S.
American accusations that Canada has not done enough to reduce forest fuel loading across the country, which is leading to larger and more destructive wildfires, has some truth to it, Mr. Gray said. But the solution is much more nuanced than Mr. Trump’s argument suggests.
Modern megafires are a result of primarily two things. Climate change is making forests drier and droughts deeper and more frequent, and creating the conditions for more frequent lightning storms.
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The other significant factor is the “fire debt” that North Americans created across fire prone landscapes through 100 years of obsessively trying to extinguish all wildfires, letting forests grow unnaturally dense. Now when they burn, they burn hotter and more intensely.
Canadian provinces lag behind some U.S. states when it comes to the use of prescribed fire to reduce fuel loads. The state of New Jersey, which is 43 times smaller than B.C., uses prescribed burning on almost five times as much land per year as B.C. does.
We “could be doing more prescribed burning and cultural burning,” Mr. Gray said.
However, more forest thinning wouldn’t have stopped the current Ontario wildfires. Those forests are too remote to be reasonable targets for fuel thinning with no roads to access them, Mr. Gray said.
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Ironically, one of the biggest impediments to fuel treatments is the economics around them.
The work costs between $1,500 to $10,000 per hectare. A 2023 report found that B.C. alone likely needs more than 390,000 hectares of forests thinned.
In order to make fuels thinning economically viable, there needs to be a market for all the wood fibre that must be removed from Canadian forests. But Americans’ tariff policies undermine any viable market for that fibre, Mr. Gray said.
“We don’t have a Canadian fire problem or an American fire problem, but we have a North America fire problem,” Mr. Gray said. “So we have to look at it in an integrated way.”